We study the Divina Commedia in High school (for three years, one "cantica" per year) and it is not actually that easy, not only for the language (that it is still a dialect of the time) but also for the interpretation of the text that is full of references to the political and social situation of the time (beginning of 1300 btw). Most of each page are actually notes...

Dante is usually credited for having chosen the Tuscany/Florence dialect to be the future Italian, later adopted by many writers and poets (that also contributed to the evolution of the language), so yes, I wouldn't say it is artificial at all, maybe the only artificial thing is the choice of a dialect over another.

And as I guess many already know many of the regional dialects survived, and in some regions more than others are still spoken. In fact an Italian is often bilingual in a sense. And if you happen to be in a book store in Italy it is not at all that rare to find a book from a contemporary author written in his local dialect.

BTW we study all of the three authors you mentioned at school ... not an easy task I assure you :P